Heatable shrinking tunnel



May 19, 1970 I H. BECK HEATABLE SHRINKING TUNNEL Uriginal Filed July 22, 1969 Fig. 1

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United States Patent ABSTRACT OF THE DISCLOSURE A longitudinal :hot-air tunnel has an inverted U-shaped hood which telescopes vertically over the base to vary the effective cross-sectional area, and is provided with adjustable plates for the end openings.

This is a continuation of application Ser. No. 746,611, filed July 22, 1969, now abandoned.

The invention concerns a heatable shrinking tunnel for goods packed in shrinkable plastic foil, in which a hood constituting the tunnel, of a generally inverted U-shaped cross section, has been arranged above a tunnel floor and covers a conveyer belt for the goods passing through said tunnel in the longitudinal direction thereof.

In the case of the known shrinking tunnels of the variety mentioned (Germany Utility Pat. 1,893,045), there is the disadvantage that because of the fixed effective cross section of the tunnel, a disproportionately large space will constantly have to be heated, for example, in the case of packing of small goods, something which is not only uneconomical but which also leads to faults in the shrunken packaging foil itself.

One of the objects of this invention is to remedy this disadvantage and to propose a shrinking tunnel whose effective cross section can be adapted to the size of the material to be packaged.

According to the invention, this task is to be solved through the fact that, in order to change the effective cross section of the tunnel, the hood constituting the tunnel encircles with its side walls the floor, in telescoping relationship, so that the hood can be adjusted as to height in relation to the floor.

In the case of a preferred design of the invention, provision has been made that for the heating of the tunnel blowers have been provided on the ceiling and the floor of said tunnel, in order to produce closed circular hot air currents wherein the direction of flow of the hot air current runs in parallel to the perpendicular plane of the longitudinal section of the tunnel and the direction of the other hot air current runs perpendicularly to this plane, in such a manner that both hot air currents commingle with each other at least partially. In this manner it is possible to achieve the advantage that independently of the effective cross section of the tunnel, the tunnel will be completely filled with hot air, and in particular across its entire width.

The subsequent description of a preferred embodiment of the invention serves, in connection with the attached drawing, for further clarification.

FIG. 1 shows a longitudinal section of a shrinking tunnel according to the invention;

FIG. 2 shows a cross section of the tunnel along the line 22 in FIG. 1; and

FIG. 3 shows a front view of the tunnel with the direction of the view coming from the left in FIG .1.

On a supporting frame 1, the floor 2 of a tunnel is fixedly mounted, which is covered by a hood 3 to complete the tunnel. In the longitudinal direction of the tunnel formed by the floor 1 and the hood 3, an air permeable conveyer track 4 runs through, which can consist, for

ice

example, of an endless conveyer belt driven in a manner (not shown in detail in the drawing), guided via rollers 5 and preferably perforated. On the air permeable conveyer belt, the goods wrapped in shrinkable plastic foil are transported through the shrinking tunnel.

The floor 2 of the tunnel and the cover 6 of the tunnel, formed by the horizontal part of the hood 3, have recesses 7 and 8, each of which the impeller of a hot air blower 9 and 10, as well as electrically heated heating elements 11 and 12, have been arranged. The recesses 7 and 8, whose shape can be recognized in FIGS. 1 and 2, form guideways for the hot air currents produced by the blowers 9 and 10. The longitudinal axis of recess 7 in the floor 2 of the tunnel runs in parallel to the longitudinal axis of said tunnel. On the other hand, the longitudinal axis of recess 8 runs in the ceiling 6 of the tunnel transversely in relation to the longitudinal axis of the tunnel. In this manner the direction of flow of hot air currents produced by the blower 9 which forms a closed circular path, indicated by arrow 13, runs parallel to the plane of the longitudinal section of the tunnel, while the direction of flow of hot air currents 14, likewise circularly closed and produced by the blower 10, is directed perpendicularly in relation to the plane of the longitudinal section of the tunnel. The two currents 13 and 14 pass through and commingle with each other approximately in the middle of the tunnel. The hot air current 13 produced by the blower 9 fills the tunnel with hot air essentially in the longitudinal direction, while the blower 10, on the basis of its transversely directed current 14, ensures that the entire cross section of the tunnel is filled with hot air. In the drawing merely one blower each has been arranged on the floor 2 of the tunnel and on the ceiling 6 of the tunnel. Howver, it is understood that if required, it would be possible to arrange several hot air blowers one behind another or one beside another on the floor or ceiling.

As shown, the hood 3 covering the tunnel has an approximately inverted U-shaped cross section and mates with its side walls 15 and 16 and the side walls 17 and 18 standing up from floor 2 in a telescoping fashion. In this manner it is possible to change the effective cross section of the tunnel by lifting or lowering hood 3 and to adapt it in regard to height to the cross sectional shape of goods that are to be wrapped, which is of considerable advantage with respect to a quick shrinkage and to a saving in heat energy.

As can be gathered from the figures, the hood 3 is attached with its side walls 15 and 16 on columns 19 and 20 which in turn rest on supports 21 or 22 in horizontally slidable relation. Columns 19 and 20 are held vertically slidably in suitable openings in the supporting frame 1, in such a manner that upon a horizontal and vertical shifting of the supports 21 and 22, they will raise or lower the hood. Using a lever, a screw spindle actuating means engages with the supports 21 and 22 in order to lift and lower the hood 3.

In the actuating means sketched in the drawing, a nut 24 shifts on a screw spindle 25 in response to turning of crank 23. The nut 24 is connected pivotally and in a manner in which it can slide on guide element 26, which is attached to one end of a toggle lever 28 mounted fixedly on a shaft 27. The other end of this toggle lever 28 is connected pivotally with the support 21. The supports 21 and 22 are also pivotally connected with levers 29, which are pivotally mounted on shaft 27 which is moved upon shifting of lever 28.

When operating crank 23, the toggle lever 28 is shifted and carries along supports 21 and 22, upward or downward, depending on the direction of rotation, as a result of which hood 3 of the tunnel can be moved up or down with the help of columns 19 and 20 which are supported horizontally slidingly on the supports 21 and 22.

It will be apparent that the change in cross section of the tunnel, just described, can be used not only in the case of a shrinking tunnel heated by means of hot air blowers, through the up-and-down movement of the hood, but just as well in the case of a shrinking tunnel which is heated in some other manner, as, for example, by means of electric heating coils.

In FIGS. 1 and 2, it will be observed that sheet metal guides 31 have been arranged inside the tunnel for angular adjustment preferably being adjustable from the outside of the hood and which have the purpose of adjusting the hot air currents correspondingly and in dependence on the shape of the goods that are to be packaged.

On both front sides of the shrinking tunnel, individually adjustable plates 32 have been arranged, by means of which the size of the inlet and outlet openings can be adapted to the shape of the material 33 that is to be packaged (see FIG. 3). In the case of the embodiment shown, these adjustable plates 32 consist of individual plates of sheet metal with longitudinal holes 34, by means of which the plates are held by adjusting screws 35 a the front sides of the hood.

Other changes and improvements in the invention may be made, which would come within the scope of the annexed claims:

I claim:

1. In heatable shrinking tunnels for packaging articles wrapped in shrinkable plastic foil, comprising an elongated floor, an endless conveyor extending longitudinally above the floor, and an elongated hood having an inverted U-shaped cross section providing downwardly extending side walls arranged in telescoping relationship to the floor, the floor of the tunnel being provided with upstanding side walls arranged in mating engagement with the side walls of the hood, elevating means for changing the position of the hood for varying the cross sectional area of tunnel and blower means including an electric heating means for circulating hot air.

2. The invention defined in claim 1, wherein said elevating means includes a pivotally mounted lever pivotally connected with a threaded spindle, a portion of the spindle projecting outwardly from the tunnel for manual rotation.

3. The invention defined in claim 1, wherein said tunnel includes blower means for circulating hot air in two closed circular paths, one of said paths originating in the upper part of the hood, the other said path originating at the floor, said paths being disposed in vertical planes disposed perpendicularly to each other, air from one path commingling with air from the other path.

4. The invention defined in claim 3, wherein adjustable 1 guide vanes disposed in the paths of said circulating air.

5. The invention defined in claim 1, wherein a plurailty of vertically adjustable plates are provided at the ends of the hood for adjusting the profile of the openings to the tunnel.

, 6. The invention defined in claim 5, wherein said plates are provided with slotted openings, and said hood includes threaded studs projecting through said openings for adjustably supporting the plates.

References Cited UNITED STATES PATENTS VOLODYMYR Y. M AYEWSKY, Primary Examiner U.S. Cl. X.R. 

